Acids and also Bases in Water
Self-ionization of WaterLiquid water is in equilibrium v solvated hydroxide and also solvated protons. We commonly use a value regarded the equilibrium consistent to define the concentration of these solvated ion in water. The water dissociation constant, Kw, is 1 x 10-14.
pH and also pOH are vital values because that acidic and straightforward solutions. These are the log base 10 of the hydrogen ion concentration or of the hydroxide ion concentration, respectively.
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pH = -log
pH and pOH are commonly used to define solutions that acids and bases in water. In pure water, the concentration of solvated protons equates to the concentration that solvated hydroxide anions and the pH is 7. Acidic solutions have a reduced pH while simple solutions have actually a higher one.
Strong AcidsStrong mountain dissociate totally in aqueous solution and also have negative values because that Ka. We have the right to assume that the
Weak AcidsWeak mountain are just partially dissociated in aqueous solution. The Ka values describe the equilibrium and the pKa = -log(Ka). Few of the weak acids space in the table below.
|hydrofluoric acid||HF H+ + F-||3.17|
|carbonic acid||H2CO3 H+ + HCO3-||6.37|
|bicarbonate||HCO3- H+ + CO3-2||10.25|
|bisulfate||HSO4- H+ + SO4-2||1.99|
|ammonium||NH4+ H+ + NH3||9.24|
|hydrogen sulfide||H2S H+ + HS-||7.0|
|water||H2O H+ + HO-||15.74|
|ammonia||NH3 H+ + NH2-||38|
Strong BasesStrong hydroxide bases are fully dissociated in aqueous solution. Other solid bases react completely with water. Strong bases include NaOH, LiOH, Ca(OH)2, NaNH2.
Weak BasesWeak bases space in equilibrium through water. The Kb values define the equilibrium and the pKb = -log(Kb).
Some weak bases space in the table below.
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|NH3||NH3 + H2O NH4+ + HO-||4.76|
|HS-||HS- + H2O H2S + HO-||7|
|CO3-2||CO3-2 + H2O HCO3- + HO-||3.75|
|SO4-2||SO4-2 + H2O HSO3-2 + HO-||12.01|
BuffersA solution containing a weak acid and also its conjugate base resists changes in pH if little amounts of acid or base space added. A systems that has equal concentrations of both the weak acid and also the conjugate base has actually a pH equal to the pKa that the acid. For example, the pH that a equipment that is 0.1 M in HSO4-2 and also 0.1 M in SO4-2 will certainly be about 2.
BackCompassTablesIndexIntroductionNextProfessor Patricia Shapley, university of Illinois, 2012